Radiant heating pad for the feet and lower limbs



B. P. M CANN Sept. 30, 1952 RADIANT HEATING PAD FOR THE FEET AND LOWERLIMBS 2 SHEETSSHEET 1 Filed May 1, 1950 BERT a MC CANN Zmnentor(Ittornegs Patented Sept. 30, 1952 RADIANT HEATING PAD FOR THE FEET ANDLOWER 'LIMBS Bert McGann, Seattle, Wash. v

Application May 1, 1950, Serial No. 159,181

4 Claims. (01. 219-19) 1 This present invention consists of a pad of asizeconvenient for resting the feet on or standing upon and which is soarranged that it is an effective radiant heating means for the feet andlower legs. The invention makes use of an insulated electricalresistance wire element which is of such resistance and length that itcan never attain, from normal electric outlets, a temperature that willbe uncomfortable to rest the feet on. Means are further provided fordirecting the greater amount of the heat generated upwardly in the formof radiant energy so that the feet canbe maintained at a comfortabletemperature and the radiant transmission from the surface of the padwill be sufiicient to keep the calves of the legs and knees warm at thesame time.

In the past, the normal means for heating dwellings, ofiices, factories,and the like, was by heating the ambient air and to circulate thiseither by conversion from radiators or by induced draft, such as isnormally considered forced air circulation. Such heating is generallyaccepted but there are so many, instances in which it does not providewarmth for the feet of those who are forced by their vocations to sit orstand at wherein steam or hot water pipes are laid in the fioors offactories, office buildings and homes, provide a very fine solution ofthis problem. However, they can only be available to a relatively smallproportion of the people, and it is to provide this type of heat tothose. persons who work or live in areas where such heating cannot bemade available that I have developed this present foot heatingpad.

This invention provides an individual heating pad of firm, durablematerialwhich can be walked on or stood on} or upon'which the feet canbe rested and which, while intended to cover only a relatively smallarea, will provide a; high degree, of comfort and improved good healthto a'large mass of working people.

For instance, the man'operating a machine tool, which nor-1 mally is ona concrete floor, can have on top of the concrete floor a pad justsufficiently large to take care of his essential movement, and this padcan be heated very economically and the heat given out by .it willcounteract the cold floors, warm his feet, and the radiant energy givenoiT from the:.upper surface of the pad'will warm the lower legs so theperson will be comfortable and thus able to achieve his highest possiblework output. There are many other persons such as those who stand watchin commercial establishments as officers of the law, or on sea-goingvessels, who thus, for the first time, have available to them, a sourceof real foot comfort. I

The principal object of this invention is to provide a heating pad thatwill provide a warm fioor' area for a person confined to a limited area.

' A further object of this invention is to provide an electric heatingpad which may be used outof-doors or in manufacturing establishments andthe like, where the same must be capable of taking unusual use withoutdamage to itself or endangering the person using the pad.

-A further object of this invention is to provide an electric heatin padmaking use of low temperature heating wire-to theend that expensivethermostatic controls, and the like, with their attendant servicingdifficulties, will be eliminated.

A further object of this invention is to provide an electric heatingpadin which the entire surface of thepad will form a transmittingsurface for radiant energy at low temperature levels so they will givereal warmth to theuser yet will never be hot enough to be uncomfortablewhen the feet are kept in close engagement therewith, as by standingthereon for long periods. V

A furtherobject of this invention is to provide a low temperatureelectric heating pad that can be economically constructed and which willhave a long, trouble-free useful life.

Further objects, advantages and capabilities will be apparent from thedescription and disclosure in the drawings, or may be comprehended orare. inherent in the device.

In the drawings:

Figure 1 is a perspective view showing how this heating pad may be usedby a desk worker;

Figure 2 is a perspective view, partly broken away and shown in section,and with a portion ofthe heating wire raised from its retaining grooveto more'fully illustrate thereof;

7 Figure 3 is an enlarged perspective viewtaken in the same sense asFigure 2 and showing the channels for the electric heating elements andthe manner in which the terminal connector is imbedded in the heatingpad so that no unex-' invention and showing the form that has been foundbestadaptable for outdoor use in that the pad will not accumulate wateron its surface;

the construction struction thereof;

Figure I is a fragmentary vertical sectional view showing an alternateinsulating arrangement;

Figure 8 is a fragmentary vertical sectional. view showing an alternateuse of reflectwemsu lation material.

Referring more particularly to the-disclosurein the drawings, thenumerals l and: H designate respectively the upper and lower layerswhich form the heating pad l2 of this invention. These two layers may bemade of any dense noncond'uctivematerial that may be madein". sheet formor molded; The basic requirement. isthat the.

sheet be relatively stiff so there-will be no tend.- ency for the edgesto-curl, yetthey should preferably be'slightly flexible when joinedtogether so that they will conform to the fioor'surfaceon which they areused even though the same is not perfectly level and smooth. It isfurther necessarythat' this materialbe of sufhcient density' so that itcan either be water-proofed' or preferably; will be-inherentlywater-proof. The materials'that have'been found mostsuitable are thetempered hard wall-boards.- l The layers may, however;be'molded-of'quite a wide range ofmaterials such asplastic; rubber, orthe synthetic rubbers. The laminated materials which combine rubber andfabric; plastic and fabric, or flexible sheet stoclgsuch as paper andthe like, are also suitable, It is. desirablethat the material fromwhich the layers are madehave some dielectric properties. and; that theybe resistant to the entrance of moisture.

Disposed betweenthe top and bottom layers is the insulated lowtemperature heating cable l4. Cables of'this order have been used forheating under special conditions for some time. Theywereoriginally.developed'for use in heating hotbed'sand' greenhousesandhave found some use in. the, radiant heating, particularly of smallhomes where they are quite often tacked to the lath. and then coveredwithplaster. Such cables are. designed for thetype of electric currentavailable. and. are so arranged, duejto the wire gauge and to theirlength, that the resistance is such that. the temperature of the cablecan neverrise aboverthe d'esignedmaximum, As the cable deterioratesafter. years of use, t he maximum temperature may not be achieved butthere is no danger of it ever going above the designed maximum. This isa very important characteristic of this. type of. heating cable in thatit permits the use of' aneconomical heat source which is not dependentupon the used thermostatic control. However, it' is conceivablev thatthe smaller type of. screw-adjusted thermostat might be used in aninstallation of this order, in the interest of.

over-all economy of construction and in the interest of, not introducinginto the unit an electrical device. that might needservice orreplacement ithas been. found. preferable to carefully design the cable.to-keep it below the maximum allowable temperature.

fromwhichthe top and bottom layers are made andtlie thickness-ofthesame, together withtlie The exact cable design. will be dependent, to adegree; uponthe materials should exceed 85 Fahrenheit, and for use, asunder a desk, where the users feet may rest at the same point for aconsiderable period this temperature should not exceed Fahrenheit Cablel4 should normally be placed in grooves as I Bcut into, preferably,thebottom layer This leaves the top layer of uniform strength throughoutits entirety and adds materially to its longer life, and further tendsto more thoroughly equal- 1Z6, the'distribution of heat throughout thetop layer. The usual form of groove [6 is indicated 7 n dotted lines inFigure 2, it being necessary to start at the cable connector and anchor18 and make'a continuous panel coil which then must have its outermostend connec e co tor 8. t d to the cable the prime need of -afoot-warming pad of this. order is for use formany kinds of floors itmay-not only be unheated, but actually may be,

in contact with the ground, as for instance, a

concrete: ground floor, and thus have its heat conducted away from itso-that it is mu than the ambient air. Under such con i ti s i tnaturally follows; it is believed, that steps should betaken to preventthe dissipation of the heat downwardly and endeavor to retain themaximumfloor radiation upwardly. To this end it is found desirable toemploy one of the .various accepted" forms of insulating material 0 s hD ne ver effective 1118211181? to employ a sheet of reflectiveinsulating material I? between the topand bottom layers. This keepsthethickness of the heat ing' pad to a minimum and does not affect its.

ability toflex slightly The refie otive material normally used-isaluminum. foil andwill readily permit sufhcient'deformation to partiallyencirclethe lower part of wire I 4* as it r ests ingrooves I6. Animproved theoretical use of the foil or sheet aluminum is shown inFigure .8 in which the, foil,

or sheet rests in a r cess in la I o yer H and theto layer issupportedby a grid of. support ribs I; This arrangement. permits the.maximum. reflectiorr from the upper surface of the sheet. An

alternate construction is sho I wn, in Figure '7 in which a fibroussheetis employed, such as 20 between the top and bottom layers. In this constructionit is found best to form insulating fibre sheet Z'dpreferablyas partof the bottom layer so that again the top 1a yer may bea sheunifoim thickness; In this form: it is define desirable to form grooveswithin fibre sheet 20- for the accommodation of' the insulated heatingwire I4; In this modified form it h as been found most effective. toemploy. rivets or through-boltsas' 22 which will be et slightl h s yinwardl OI the surface of the topv andbottom layer e. This makes itpossible. to. obtain a good seal at-the igllllgggged 24 soliihat theheating cable: can' be e as'we as the fibro intrusion of moisture.ls-board, from-the Normally it has been found com parativel eas tothbondthe. upper and lower layers tog ethei ei or by heat, fllSlOI1,- or bythe application of adhesives suitable for the surfaces joined toge her.There. is,- however, no real objection to the employment of through-rivets or flush boltilriegcetslggiyiygg the body of thepad if thatappears ecause of the t ethe two layers- 31p of sheets used in In Figure2 the preferred form of thi heating pad is shown as adapted to the -u fthosepersons who are well shielded from the weather or dampness.However, it has been found. thatmany persons who must work under adverseweather conditions; are actually the ones who are urgently in need of adevice of this order, and to serve this field, there has beenillustrated in Figures 4 and 5, a modified form of structure, modifiedonly however, in that the pad is pierced with a large number ofregularly positioned openings so as to reduce the surface and to preventthe accumulation of water thereon by allowing it to drain off. In otherwords, a form of screening or open mat is provided which has been foundmost adaptable for the outside use. The various openings 30 are, ofcourse, so disposed as to be in between the loops of cable [4 so thatthe structure. basically, is the same as shown in Figure 2. Thecross-sectional view of Figure 5 shows generally the structure where thetop and bottom layers are fused together, as can be achieved with manyof the plastics and certain of the rubber substitutes.

It is readily apparent that a pad of this order will be very simple touse. Normally, the wattage employed is relatively low and thetemperature, of course. will vary somewhat with the conditions of use.For inside use it normally will not exceed 100 or 200 watts. and foroutside use will rarely exceed 300 watts, due to the fact that the Ipads need to cover only 3 or 4 sduare feet. The pad functions in usevery similarly to a radiantly heated floor. In other words, the entireupper, or top layer. becomes heated to the maximum allowabletemperature. normally 80 Fahrenheit. and the top surface then becomes aheat transmitter. The heat transfer. of course. follows the same laws asany other form of heating and takes fully into acco nt the naturaltendency of warm air to rise. This causes a conduction transfer whichmay amount to as much as of the total heat transmitted and leave forradiant transfer approximately 55% of the total. It will thus be aparent. it is believed. that not only will the soles of the feet bewarm. but a ood deal of heat will be assed on to the lower limbs.

It is believed that it will be clearly apparent from the abovedescription and the disclosure in the drawin s that the invent on comrehends a novel construction of a radiant heating pad for the feet andlower limbs.

Having thus disclosed the invention, I claim:

1. A radiant heating pad for the feet and lower limbs, comprising: a toplayer and a bottom layer of durable sheet material having dielectric andwater resistant properties. said top and bottom layer being fixedlysecured together: an insulated, low temperature heating cable coiledbetween said la ers to produce a tem erature on the u per surface ofsaid top layer within a range of temperatures comfortable to feet,resting on the pad, said cable having a single wire of such small gaugeand being of such length that it cannot heat be ond a low designedmaximum temperature: said bottom laver being configured to accept saidheatin cable to lie in a plane below said top layer: a cable connectorpositioned between said top laver and bottom layer and both ends of saidcable being connected to said connector making a continuous panel coil:and a sheet of heat-reflective. metal foil on the up er surface of saidbottom la er and pressed into the configurations in said bottom laver tolie below said heatin cable.

2. A radiant heating pad for the feet and lower limbs. comprising: a toplayer and a bottom layer of durable sheet material having dielectric andwater resistant properties: an insulated. low tem perature heating cablecoiled between said layers and lying in a common plane below the lowersurface of said top layer to produce a temperature on the upper surfaceof said top layer within a range of temperatures comfortable to feet,resting on the pad, said cable having a single wire of such small gaugeand being of such length that it cannot heat beyond a low designedmaximum temperature; said cable having means for connecting the cable toa source of electricity; insulating material disposed between saidlayers and below said heating cable only; said bottom layer beingconfigured to accept said heating cable and said insulating material.

3. A radiant heating pad for the feet and lower limbs, comprising: adurable thin heating pad of a size to accommodate the feet of a person;a low temperature heating cable coiled in said heating pad and lying ina common horizontal plane to produce a substantially even temperature onthe upper surface of the heating pad within a range of temperaturescomfortable to feet; resting on the pad, said cable having a single wireof such small gauge and being of such length that it cannot heat beyonda low designed maximum temperature; said cable having a dielectriccoating insulating said cable to prevent conduction of electricity fromsaid cable to the surfaces of .said pad; said cable having means forconnecting the cable to a source of electricity; and said pad having asingle sheet of reflective insulating material positioned under saidcable to reflect heat from said cable upward.

4. A radiant heating pad for the feet and lower limbs, comprising: adurable fiat, thin heating pad of a size to accommodate the feet of aperson, said pad having separate upper and lower members with theirexterior faces forming the top and bottom surfaces of said pad; a lowtemperature heating cable coiled in said heating pad below the lowersurface of said upper member to produce a substantially even temperatureon the upper surface of the heating pad within a range of temperaturescomfortable to feet. resting on the pad, said cable having a single wireof such small gauge and being of such length that it cannot heat beyonda low designed maximum temperature; said cable having a dielectriccoating insulating said cable to prevent conduction of electricity fromsaid cable to the surfaces of said pad; said cable having means at thejuncture of its two ends for connecting the cable to a source ofelectricity; and a single sheet of heat insulating material disposedbetween said cable and said lower member.

BERT P. McCANN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 12,782 Landry Apr. 21, 19081,263,350 Schneider Apr. 16, 1918 1,703,640 Schmidt-Predari Feb. 26,1929 1,994,759 Dermott Mar. 19, 1935 FOREIGN PATENTS Number Country Date13,989 Great Britain June 17, 1913 118,300 Great Britain Aug. 19, 1918251,853 Switzerland Nov. 30, 1947 488,826 Great Britain July 14, 1938OTHER REFERENCES Modern Plastics, pages 108-109, August 1946.

